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What is an Electric Fuel Pump?

New low-pressure electric fuel pumps can help prevent vapor lock.
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  • Written By: Alexis W.
  • Edited By: Jenn Walker
  • Last Modified Date: 03 November 2014
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An electric fuel pump is a tool used to power a vehicle's engine system by providing fuel through the use of electronic means. The electric pump is a post-World-War-II innovation that made cars more efficient, reliable and affordable. The electric fuel pump is an alternative to a manual fuel pump system and is widely considered to be a better use of technology with regards to the function and operation of motor vehicles.

An electric fuel pump is small and thermally insulated to prevent sparking. Generally, it consists of a 12-volt electric motor attached to a pump assembly that pulls fuel in as the motor spins, and pushes it out through a different line that goes to the engine compartment. The fuel may pass through a fuel filter after it leaves the pump, or it may be filtered before the pump. The assembly runs at a constant pressure to allow for optimum fuel delivery to the engine without interruption and also to prevent air from getting into the fuel lines and causing problems.

Old-style fuel pumps were manual pumps that ran because the engine’s rotation caused a small arm to lift and pull fuel into a float bowl. After the fuel entered the float bowl, it could be sucked by vacuum into the carburetor to be delivered to the engine. This system was effective, but could cause problems.

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Vapor lock, which occurred when the vehicle was stopped, then attempted to be started again, was one major issue with manual fuel pumps. Vapor lock occurred when hot, tiny bubbles were able to form in the fuel lines. The bubbles would not pass through the mechanical fuel pump and this would, in turn, cause the vehicle not to start. This became a common problem in the 1960s and early 1970s.

The electric fuel pump, a modern alternative to the manual pump, is mounted inside the vehicle’s fuel tank. Instead of a manual mechanism activated by the engine's rotation, a small electric pump is powered by the vehicle’s electrical system. This means the pump is independent of the operation of the engine.

The electric fuel pump can deliver more fuel at a higher pressure to help the engine get all of the fuel that it needs. Because the electric fuel pump pressurizes the fuel system before the engine is started, there is always a constant supply of fuel available in the lines at the proper pressure. There are also no air bubbles to cause vapor lock.

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miriam98
Post 2

@nony - Yeah, fuel pump prices are not cheap. You might be able to find aftermarket parts online if you want to go that route. However you raise a good point that both the fuel pump and the fuel filter can go bad.

One way to prevent the fuel filter from going bad too soon is not to let your car get too low on gas before filling it. Don’t wait until it gets near empty. If it’s almost empty, then the car is dredging up gunk from the bottom of the tank, and this will clog up the filter.

Then you have a situation that is similar in some sense to what happened with mechanical fuel pumps, where vapor bubbles were clogging things up as the article says. So fill up your car when it gets to about a quarter of a tank and you should be good.

nony
Post 1

I think it should be obvious that electric fuel pumps for cars are very important. Given that this is so, I think it’s even more important to recognize the warning signs that your fuel pump is going bad.

I didn’t know much about cars myself so I found out the hard way. I had bought this very old Honda Civic and everything was going along just smooth for the first months. Then something weird happened.

I started losing power out on the highway. At first it was temporary and I would have to give the car more gas to keep it going at regular speed. But then it got worse, to the point where I could barely muster 45 miles per hour on the highway!

I had a mechanic check it and sure enough it was the fuel pump. I was hoping it was just the filter because the filter would have been so much cheaper.

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